Apparatus using multiple beams of charged particles

ABSTRACT

Disclosed herein is an apparatus comprising: a first electrically conductive layer; a second electrically conductive layer; a plurality of optics element s between the first electrically conductive layer and the second electrically conductive layer, wherein the plurality of optics elements are configured to influence a plurality of beams of charged particles; a third electrically conductive layer between the first electrically conductive layer and the second electrically conductive layer; and an electrically insulating layer physically connected to the optics elements, wherein the electrically insulating layer is configured to electrically insulate the optics elements from the first electrically conductive layer, and the second electrically conductive layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority of U.S. application 62/492,043 whichwas filed on Apr. 28, 2017 and which is incorporated herein in itsentirety by reference.

TECHNICAL FIELD

This disclosure relates to an apparatus for inspecting or observingsamples such as wafers and masks used in a device manufacturing processsuch as the manufacture of integrated circuits (ICs).

BACKGROUND

A device manufacturing process may include applying a desired patternonto a substrate. A patterning device, which is alternatively referredto as a mask or a reticle, may be used to generate the desired pattern.This pattern can be transferred onto a target portion (e.g., includingpart of, one, or several dies) on the substrate (e.g., a silicon wafer).Transfer of the pattern is typically via imaging onto a layer ofradiation-sensitive material (resist) provided on the substrate. Asingle substrate may contain a network of adjacent target portions thatare successively patterned. A lithographic apparatus may be used forthis transfer. One type of lithographic apparatus is called a stepper,in which each target portion is irradiated by exposing an entire patternonto the target portion at one time. Another type of lithographyapparatus is called a scanner, in which each target portion isirradiated by scanning the pattern through a radiation beam in a givendirection (the “scanning”-direction) while synchronously scanning thesubstrate parallel or anti parallel to this direction. It is alsopossible to transfer the pattern from the patterning device to thesubstrate by imprinting the pattern onto the substrate.

In order to monitor one or more steps of the device manufacturingprocess (e.g., exposure, resist-processing, etching, development,baking, etc.), a substrate patterned by the device manufacturing processor a patterning device used therein may be inspected, in which one ormore parameters of the substrate or the patterning device may bemeasured. The one or more parameters may include, for example, edgeplace errors (EPEs), which are distances between the edges of thepatterns on the substrate or the patterning device and the correspondingedges of the intended design of the patterns. Inspection may also findpattern defects (e.g., failed connection or failed separation) anduninvited particles.

Inspection of substrates and patterning devices used in a devicemanufacturing process can help to improve the yield. The informationobtained from the inspection can be used to identify defects, or toadjust the device manufacturing process.

SUMMARY

Disclosed herein is an apparatus comprising: a first electricallyconductive layer; a second electrically conductive layer; a plurality ofoptics elements between the first electrically conductive layer and thesecond electrically conductive layer, wherein the plurality of opticselements are configured to influence a plurality of beams of chargedparticles; a third electrically conductive layer between the firstelectrically conductive layer and the second electrically conductivelayer; and an electrically insulating layer physically connected to theoptics elements, wherein the electrically insulating layer is configuredto electrically insulate the optics elements from the first electricallyconductive layer, and the second electrically conductive layer.

According to an embodiment, the third electrically conductive layercomprises a plurality of holes, wherein the holes house the opticselements.

According to an embodiment, the optics elements are electricallyinsulated from the third electrically conductive layer.

According to an embodiment, the third electrically conductive layer iselectrically connected to the first electrically conductive layer, thesecond electrically conductive layer, or both.

According to an embodiment, the first electrically conductive layer andthe second electrically conductive layer comprise openings, wherein theopenings and the optics elements collectively form paths of theplurality of beams of charged particles.

According to an embodiment, the openings have an inverted funnel orcounterbore shape.

According to an embodiment, the third electrically conductive layer ispositioned between at least two of the optics elements.

According to an embodiment, the first electrically conductive layer, thesecond electrically conductive layer, and the third electricallyconductive layer collectively form cavities that accommodate the opticselements, wherein the cavities are configured to electrically shield theoptics elements from one another.

According to an embodiment, the electrically insulating layer comprisesdiscrete portions, each of which is physically connected to one of theoptics elements.

According to an embodiment, the electrically insulating layer isphysically connected to the first electrically conductive layer, thesecond electrically conductive layer, or the third electricallyconductive layer.

According to an embodiment, the electrically insulating layer isconfigured to provide mechanical support to the optics elements.

According to an embodiment, the electrically insulating layer ispositioned upstream with respect to the optics elements.

According to an embodiment, the electrically insulating layer ispositioned downstream with respect to the optics elements.

According to an embodiment, the electrically insulating layer extendsbetween the third electrically conductive layer and the firstelectrically conductive layer.

According to an embodiment, the electrically insulating layer insulatesthe first electrically conductive layer from the third electricallyconductive layer, the second electrically conductive layer, and theoptics elements.

According to an embodiment, the electrically insulating layer comprisesan electrically conductive via through the electrically insulatinglayer, wherein the electrically conductive via electrically connects thefirst electrically conductive layer to the third electrically conductivelayer.

According to an embodiment, the electrically conductive via encircles acavity formed by the first electrically conductive layer, the secondelectrically conductive layer, and the third electrically conductivelayer and housing one of the optics elements.

According to an embodiment, the electrically insulating layer extendsbetween the third electrically conductive layer and the secondelectrically conductive layer.

According to an embodiment, the electrically insulating layer insulatesthe second electrically conductive layer from the third electricallyconductive layer, the first electrically conductive layer, and theoptics elements.

According to an embodiment, the electrically insulating layer comprisesan electrically conductive via through the electrically insulatinglayer, wherein the electrically conductive via electrically connects thesecond electrically conductive layer to the third electricallyconductive layer.

According to an embodiment, the first electrically conductive layer, thesecond electrically conductive layer and the third electricallyconductive layer comprise a semiconductor or a metal.

According to an embodiment, the optics elements are selected from agroup consisting of a lens, a stigmator, a deflector, and a combinationthereof.

According to an embodiment, the optics elements are configured togenerate an electric field selected from a group consisting of around-lens electrostatic field, an electrostatic dipole field and anelectrostatic quadrupole field.

According to an embodiment, at least one of the optics elementscomprises multiple poles.

According to an embodiment, the first electrically conductive layer, thesecond electrically conductive layer and the third electricallyconductive layer are configured to reduce crosstalk or fielddistribution deformation of the optics elements.

According to an embodiment, the apparatus further comprises a detectorconfigured to capture a signal produced from an interaction of the beamsand a sample.

According to an embodiment, the signal comprises secondary electrons orbackscattered electrons, Auger electrons, X-ray, or cathodoluminescence.

According to an embodiment, the charged particles comprise electrons.

Disclosed herein is an apparatus comprising: a first electricallyconductive layer; a second electrically conductive layer; a plurality ofoptics elements between the first electrically conductive layer and thesecond electrically conductive layer, wherein the plurality of opticselements are configured to influence a plurality of beams of chargedparticles; a third electrically conductive layer between the firstelectrically conductive layer and the second electrically conductivelayer; and an electrically insulating layer physically connected to theoptics elements, wherein the electrically insulating layer is configuredto electrically insulate the optics elements from the first electricallyconductive layer, and the second electrically conductive layer; whereinthe electrically insulating layer extends between the third electricallyconductive layer and the first electrically conductive layer, or betweenthe third electrically conductive layer and the second electricallyconductive layer.

Disclosed herein is an apparatus comprising: a first electricallyconductive layer; a second electrically conductive layer; a plurality ofoptics elements between the first electrically conductive layer and thesecond electrically conductive layer, wherein the plurality of opticselements are configured to influence a plurality of beams of chargedparticles; a third electrically conductive layer between the firstelectrically conductive layer and the second electrically conductivelayer; an electrically insulating layer physically connected to theoptics elements, wherein the electrically insulating layer is configuredto electrically insulate the optics elements from the first electricallyconductive layer, and the second electrically conductive layer; and afourth electrically conductive layer in contact with and upstream to thefirst electrically conductive layer.

Disclosed herein is an apparatus comprising: a first electricallyconductive layer; a second electrically conductive layer; a plurality ofoptics elements between the first electrically conductive layer and thesecond electrically conductive layer, wherein the plurality of opticselements are configured to influence a plurality of beams of chargedparticles; a third electrically conductive layer between the firstelectrically conductive layer and the second electrically conductivelayer; an electrically insulating layer physically connected to theoptics elements, wherein the electrically insulating layer is configuredto electrically insulate the optics elements from the first electricallyconductive layer, and the second electrically conductive layer; and afifth electrically conductive layer in contact with and downstream tothe second electrically conductive layer.

Disclosed herein is a system comprising: a source configured to producecharged particles; an optics system configured to generate with thecharged particles multiple probe spots on a surface of a sample and toscan the probe spots on the surface, the optics system comprising any ofthe above apparatuses.

According to an embodiment, the source is an electron gun.

BRIEF DESCRIPTION OF FIGURES

FIG. 1A schematically shows an apparatus that can carry out chargedparticle beam inspection using multiple beams of charge particles, wherethe charged particles in the multiple beams are from a single source (a“multi-beam” apparatus).

FIG. 1B schematically shows an alternative multi-beam apparatus.

FIG. 1C schematically shows an alternative multi-beam apparatus.

FIG. 2A schematically shows crosstalk between two optics elements in asource-conversion unit in a multi-beam apparatus.

FIG. 2B schematically shows a cross-sectional view along section A-A ofFIG. 2A.

FIG. 3A, FIG. 3B, FIG. 3C, FIG. 3D, FIG. 3E and FIG. 3F eachschematically show a portion of the source-conversion unit in amulti-beam apparatus, according to an embodiment.

FIG. 3G schematically shows a cross-sectional view along section B-B ofFIG. 3C or FIG. 3D.

FIG. 3H and FIG. 3I each schematically show a portion of thesource-conversion unit of a multi-beam apparatus, according to anembodiment.

FIG. 4A schematically shows that two of the portions of FIG. 3C arestacked.

FIG. 4B shows another example of the source-conversion unit, which issimilar to the source-conversion unit in FIG. 4A except that one of thetwo portions is the portion in FIG. 3H.

FIG. 5A schematically shows that three of the portions of FIG. 3C amstacked.

FIG. 5B shows another example of the source-conversion unit, which issimilar to the source-conversion unit in FIG. 5A except that one of thethree portions is the portion in FIG. 3I1.

FIG. 6A schematically shows that three of the portions of FIG. 3I) arestacked.

FIG. 6B shows another example of the source-conversion unit, which issimilar to the source-conversion unit in FIG. 6A except that one of thethree portions is the portion in FIG. 3I.

FIG. 7A schematically shows a source-conversion unit including three ofthe portions of FIG. 3C stacked on one another and a portion of FIG. 3Dupstream.

FIG. 7B shows another example of the source-conversion unit, which issimilar to the source-conversion unit in FIG. 7A except that one of thethree portions is the portion in FIG. 3H.

DETAILED DESCRIPTION

There are various techniques for inspecting the sample (e.g., asubstrate and a patterning device). One kind of inspection techniques isoptical inspection, where a light beam is directed to the substrate orpatterning device and a signal representing the interaction (e.g.,scattering, reflection, diffraction) of the light beam and the sample isrecorded. Another kind of inspection techniques is charged particle beaminspection, where a beam of charged particles (e.g., electrons) isdirected to the sample and a signal representing the interaction (e.g.,secondary emission and back-scattered emission) of the charged particlesand the sample is recorded.

Charged particle beam inspection may have higher resolution than opticalinspection due to the shorter wavelengths of the charged particles usedin the former than the light used in the latter. As the dimensions ofthe patterns on the substrate and the patterning device become smallerand smaller as the device manufacturing process evolves, chargedparticle beam inspection becomes more widely used. The throughput ofcharged particle beam inspection is relatively low due to interactions(e.g., the Coulomb effect) among the charged particles used therein.More than one beam of charged particles may be used to increase thethroughput.

In an example, multiple beams of charged particles can simultaneouslyscan multiple regions on a sample. The scanning of the multiple beamsmay be synchronized or independent. The multiple regions may haveoverlaps among them or may be isolated from one another. Signalsgenerated from the interactions of the beams and the sample may becollected by multiple detectors. The number of detectors may be lessthan, equal to, or greater than the number of the beams. The multiplebeams may be individually controlled or collectively controlled.

Multiple beans of charged particles may form multiple probe spots on asurface of a sample. The probe spots can respectively or simultaneouslyscan multiple regions on the surface. The charged particles of each beammay generate signals from the locations of the probe spots. One exampleof the signals is secondary electrons. Secondary electrons usually haveenergies less than 50 eV. Another example of the signals isbackscattered electrons when the charged particles of the beams areelectrons. Backscattered electrons usually have energies close to ladingenergies of the electrons of the beams. The signals from the locationsof the probe spots may be respectively or simultaneously collected bymultiple detectors.

The multiple beams may be from multiple sources respectively, or from asingle source. If the beams are from multiple sources, multiple columnsmay scan and focus the beams onto the surface, and the signals generatedby the beams may be detected by detectors in the columns, respectively.An apparatus using beams from multiple sources may be called as amulti-column apparatus. The columns can be either independent or share amulti-axis magnetic or electromagnetic-compound objective lens (see U.S.Pat. No. 8,294,095, whose disclosure is hereby incorporated by referencein its entirety). The probe spots generated by a multi-column apparatusmay be spaced apart by a distance as large as 30-50 mm.

If the beams are from a single source, a source-conversion unit may beused to form multiple virtual or real images of the single source. Eachof the images and the single source may be viewed as an emitter of abeam (also called a “beamlet” as all of the beamlets are from the samesource). The source-conversion unit may have an electrically conductivelayer with multiple openings that can divide the charged particles fromthe single source into multiple beams (also called “beamlets”). Thesource-conversion unit may have optics elements that can influence thebeamlets to form multiple virtual or real images of the single source.Each of the images can be viewed as a source that emits one of thebeamlets. The beamlets may be spaced apart by a distance of micrometers.A single column, which may have a projection system and a deflectionscanning unit, may be used to scan and focus the beamlets on multipleregions of a sample. The signals generated by the beamlets may berespectively detected by multiple detection elements of a detectorinside the single column. An apparatus using beams from a single sourcemay be called as a multi-beam apparatus.

There are at least two methods to form the images of the single source.In the first method, each optics element has an electrostatic micro-lensthat focuses one beamlet and thereby forms one real image. (see, e.g.,U.S. Pat. No. 7,244,949, whose disclosure is hereby incorporated byreference in its entirety). In the second method, each optics elementhas an electrostatic micro-deflector which deflects one beamlet therebyforms one virtual image (see, e.g., U.S. Pat. No. 6,943,349 and U.S.patent application Ser. No. 15/065,342, whose disclosures are herebyincorporated by reference in their entirety). Interactions (e.g., theCoulomb effect) among the charged particles in the second method may beweaker than that in the first method because a real image has a highercurrent density.

FIG. 1A schematically shows an apparatus 400 that can carry out chargedparticle beam inspection using multiple beams of charge particles, wherethe charged particles in the multiple beams are from a single source (amulti-beam apparatus). The apparatus 400 has a source 401 that canproduce charged particles in free space. In an example, the chargedparticles are electrons and the source 401 is an electron gun. Theapparatus 400 has an optics system 419 that can generate with thecharged particles multiple probe spots on a surface of a sample 407 amidscan the probe spots on the surface of the sample 407. The optics system419 may have a condenser lens 404 and a main aperture 405 upstream ordownstream with respect to the condenser lens 404. The expression“Component A is upstream with respect to Component B” as used hereinmeans that a beam of charged particles would reach Component A beforereaching Component B in normal operation of the apparatus. Theexpression “Component B is downstream with respect to Component A” asused herein means that a beam of charged particles would reach ComponentB after reaching Component A in normal operation of the apparatus. Theoptics system 419 has a source-conversion unit 410 configured to formmultiple virtual images (e.g., virtual images 402 and 403) of the source401. The virtual images and the source 401 each can be viewed as anemitter of a beamlet (e.g., beamlets 431, 432 and 433). Thesource-conversion unit 410 may have an electrically conductive layer 412with multiple openings that can divide the charged particles from thesource 401 into multiple beamlets, and optics elements 411 that caninfluence the beamlets to form the virtual images of the source 401. Theoptics elements 411 may be micro-deflectors configured to deflect thebeamlets. The electric current of the beamlets may be affected by thesizes of the openings in the electrically conductive layer 412 or thefocusing power of the condenser lens 404. The optics system 419 includesan objective lens 406 configured to focus the multiple beamlets andthereby form multiple probe spots onto the surface of the sample 407.The source-conversion unit 410 may also have micro-compensatorsconfigured to reduce or eliminate aberrations (e.g., field curvature andastigmatism) of the probe spots.

FIG. 1B schematically shows an alternative multi-beam apparatus. Thecondenser lens 404 collimates the charged particles from the source 401.The optics elements 411 of the source-conversion unit 410 may comprisemicro-compensators 413. The micro-compensators 413 may be separate frommicro-deflectors or may be integrated with micro-deflectors. Ifseparated, the micro-compensators 413 may be positioned upstream to themicro-deflectors. The micro-compensators 413 are configured tocompensate for off-axis aberrations (e.g., field curvature, astigmatismand distortion) of the condenser lens 404 or the objective lens 406. Theoff-axis aberrations may negatively impact the sizes or positions of theprobe spots formed by off-axis (i.e., being not along the primaryoptical axis of the apparatus) beamlets. The off-axis aberrations of theobjective lens 406 may not be completely eliminated by deflection of thebeamlets. The micro-compensators 413 may compensate for the residueoff-axis aberrations (i.e., the portion of the off-axis aberrations thatcannot be eliminated by deflection of the beamlets) of the objectivelens 406, or non-uniformity of the sizes of the probe spots. Each of themicro-compensators 413 is aligned with one of the openings in theelectrically conductive layer 412. The micro-compensators 413 may eachhave four or more poles. The electric currents of the beamlets may beaffected by the sizes of the openings in the electrically conductivelayer 412 and/or the position of the condenser lens 404.

FIG. 1C schematically shows an alternative multi-beam apparatus. Theoptics elements 411 of the source-conversion unit 410 may comprisepre-bending micro-deflectors 414. The pre-bending micro-deflectors 414are micro-deflectors configured to bend the beamlets before they gothrough the openings in the electrically conductive layer 412.

Additional descriptions of apparatuses using multiple beams of chargeparticles from a single source may be found in U.S. Patent ApplicationPublications 2016/0268096, 2016/0284505 and 2017/0025243, U.S. Pat. No.9,607,805, U.S. patent application Ser. Nos. 15/365,145, 15/213,781,15/216,258 and 62/440,493, and PCT Application PCT/US17/15223, thedisclosures of which are hereby incorporated by reference in theirentirety.

When two optics elements (e.g., the micro-deflectors ormicro-compensators in FIG. 1A, FIG. 1B or FIG. 1C) in asource-conversion unit (e.g., the source-conversion unit 410 in FIG. 1A,FIG. 1B or FIG. 1C) are close to one another, there may be crosstalkbetween them. Namely, the electric field caused by one optics elementmay extend into the beam path of another optics element and affect thebeam transmitting through the other optics element. For example, themicro-deflectors in the source-conversion unit 410 may bend the beamletsby electric fields and the electric field generated by onemicro-deflector may extend into the beam path of a neighboringmicro-deflector, thereby causing the beamlet through the neighboringmicro-deflector to bend by an amount in addition to the bending causedby the electric field generated by the neighboring micro-deflector.Similarly, for example, the electric field (e.g., a quadrupole field ora round-lens field) generated by one of the micro-compensators in thesource-conversion unit 410 may extend into the beam path of aneighboring micro-compensator, and thereby influencing the beamletthrough the neighboring micro-compensator, by an amount in addition tothe influence caused by the electric field generated by the neighboringmicro-compensator.

The crosstalk tends to be more serious if the optics elements are closerto one another (e.g., integrated into one wafer or a stack of wafers).As an example, FIG. 2A schematically shows crosstalk between two opticselements 611 and 612 integrated in a stack of wafers. FIG. 2Bschematically shows a cross-sectional view along section A-A of FIG. 2A.The optics elements 611 and 612 are attached to an insulation layer 616.There is an electrically conductive plate 617 with openings (e.g.,circular in shape) upstream to the optics elements 611 and 612, or anelectrically conductive plate 618 with openings (e.g., circular inshape) downstream to the optics elements 611 and 612. The opticselements 611 and 612 may have circular electrodes or multiple poles.When the optics element 611 is set at a potential different from thepotentials of the conductive plates 617 and 618, an electric field isgenerated to influence (e.g., compensate for field curvature aberrationof) a beamlet transmitting along a beam path 613 through the opticselement 611. The equipotential lines 615 in FIG. 2A and FIG. 2Brepresent an electric field when the conductive plates 617 and 618 andthe optics element 612 are at the same potential that is different fromthe potential of the optics element 611, the openings in theelectrically conductive plates 617 and 618 are circular, and the opticselements 611 and 612 have circular electrodes. As shown by the extensivesize of the equipotential lines 615, the electric field extends into abeam path 614 through the optics element 612. A beamlet passing throughthe optics element 612 thus may be affected not only by the electricfield the optics element 612 generates but also by the electric fieldthe optics element 611 generates, i.e., optics elements 611 and 612 havecrosstalk.

As shown in FIG. 2B, the equipotential lines 615 are not axisymmetricbecause the structure surrounding the optics element 611 is notaxisymmetric. Hence the electric field the optics element 611 generatescomprises not only an axisymmetric component (also called a round-lensfield), which compensates for the field curvature aberration, but alsohigh order rotation-symmetric components such as a deflection field anda stigmator field. The high order components add aberrations to thebeamlet passing through the optics element 611.

FIG. 3A and FIG. 3B each schematically show a portion 700 of asource-conversion unit of a multi-beam apparatus, according to anembodiment. The portion 700 has multiple optics elements 710 (e.g.,micro-deflectors, micro-lenses, micro-stigmators, micro-compensators)sandwiched between a first electrically conductive layer 720 and asecond electrically conductive layer 740. The first electricallyconductive layer 720 and the second electrically conductive layer 740have openings that, collectively with the optics elements 710, formpaths (e.g., paths 701, 702 and 703) of the beamlets. The portion 700also has a third electrically conductive layer 730 with multiple holesthat house the optics elements 710. The third electrically conductivelayer 730 extends between the first electrically conductive layer 720and the second electrically conductive layer 740. The third electricallyconductive layer 730 is electrically connected to the first electricallyconductive layer 720, or the second electrically conductive layer 740,or both. The third electrically conductive layer 730 is positionedbetween at least two of the optics elements 710, i.e., a plane the beampaths of the two optics elements 710 are on crosses the thirdelectrically conductive layer 730. The walls among the holes of thethird electrically conductive layer 730 can provide electrostaticshielding among the optics elements 710. The portion 700 has anelectrically insulating laver 750. The electrically insulating layer 750is physically connected to the optics elements 710. For example, theelectrically insulating layer 750 may have discrete portions, each ofwhich is physically connected to one of the optics elements 710. Theelectrically insulating layer 750 is physically connected to the firstelectrically conductive layer 720, the second electrically conductivelayer 740, or the third electrically conductive layer 730. Theelectrically insulating layer 750 can provide mechanical support to theoptics elements 710 and electrically insulate the optics elements 710from the first electrically conductive layer 720, the secondelectrically conductive layer 740, and the third electrically conductivelayer 730. The first electrically conductive layer 720, the secondelectrically conductive layer 740, and the third electrically conductivelayer 730 collectively form cavities 760 electrically shielded from oneanother, where each of the cavities 760 accommodates one of the opticselements 710. The cavities 760 may have circular cross-sectional shape.The first electrically conductive layer 720, the second electricallyconductive layer 740, and the third electrically conductive layer 730may also be magnetically conductive to magnetically shield the beampaths from outside stray magnetic fields. In the examples shown in FIG.3A and FIG. 3B, the electrically insulating layer 750 is positionedupstream and downstream with respect to the optics elements 710,respectively. In the examples shown in FIG. 3A and FIG. 3B, the thirdelectrically conductive layer 730 is electrically connected to both thefirst electrically conductive layer 720 and the second electricallyconductive layer 740.

FIG. 3C and FIG. 3D each schematically show a portion 700 of asource-conversion unit of a multi-beam apparatus, according to anembodiment. The example shown in FIG. 3C is the same as the example inFIG. 3A, except that the electrically insulating layer 750 extendsbetween the third electrically conductive layer 730 and the firstelectrically conductive layer 720. The electrically insulating layer 750electrically insulates the first electrically conductive layer 720 fromthe optics elements 710. The electrically insulating layer 750electrically may also insulate the first electrically conductive layer720 from the third electrically conductive layer 730, and the secondelectrically conductive layer 740. The electrically insulating layer 750may have one or more electrically conductive vias 723 through it and theconductive vias 723 electrically connect the first electricallyconductive layer 720 to the third electrically conductive layer 730. Theelectrically insulating layer 750 can be very thin, such as less than100 microns, less than 50 microns or less than 10 microns. Theelectrically insulating layer 750 can be an oxide, nitride or any othersuitable material.

The example shown in FIG. 3D is the same as the example in FIG. 3I,except that the electrically insulating layer 750 extends between thethird electrically conductive layer 730 and the second electricallyconductive layer 740. The electrically insulating layer 750 electricallyinsulates the second electrically conductive layer 740 from the opticselements 710. The electrically insulating layer 750 may also insulatethe second electrically conductive layer 740 from the third electricallyconductive layer 730 and the first electrically conductive layer 720.The electrically insulating layer 750 may have one or more electricallyconductive vias 723 through it and thereby electrically connect thesecond electrically conductive layer 740 to the third electricallyconductive layer 730 by the one or more electrically conductive vias 723and the conductive vias 723 electrically connect the second electricallyconductive layer 740 to the third electrically conductive layer 730. Theelectrically insulating layer 750 can be very thin, such as less than100 microns, less than 50 microns or less than 10 microns. Theelectrically insulating layer 750 can be an oxide, nitride or any othersuitable material.

FIG. 3E and FIG. 3F each schematically show a portion 700 of asource-conversion unit of a multi-beam apparatus, according to anembodiment. The examples shown in FIG. 3E and FIG. 3F are the same asthe examples in FIG. 3C and FIG. 3D, respectively, except that theelectrically insulating layer 750 has an electrically conductive via 723encircling each of the cavities 760 and the electrically conductive via723 electrically connects the third electrically conductive layer 730 tothe first electrically conductive layer 720 or the second electricallyconductive layer 740. FIG. 3G schematically shows a cross-sectional viewalong section B-B of FIG. 3C or FIG. 3D.

FIG. 3I1 schematically shows a portion 700 of a source-conversion unitof a multi-beam apparatus, according to an embodiment. The example shownin FIG. 3H is the same as the example in FIG. 3C, except that theportion 700 additional has a fourth electrically conductive layer 721upstream to the first electrically conductive layer 720. The fourthelectrically conductive layer 721 may be directly bonded to the firstelectrically conductive layer 720. The fourth electrically conductivelayer 721 and the first electrically conductive layer 720 may have thesame material. The fourth electrically conductive layer 721 has openingswhose sidewall is thinned to reduce scattering of charged particlesthereon. To thin the sidewall, the openings can have an inverted funnelor counterbore shape as shown in FIG. 3H.

FIG. 3I schematically shows a portion 700 of a source-conversion unit ofa multi-beam apparatus, according to an embodiment. The example shown inFIG. 3I is the same as the example in FIG. 3D, except that the portion700 additional has a fifth electrically conductive layer 741 downstreamto the second electrically conductive layer 740. The fifth electricallyconductive layer 741 may be directly bonded to the second electricallyconductive layer 740. The fifth electrically conductive layer 741 andthe second electrically conductive layer 740 may have the same material.The fifth electrically conductive layer 741 has openings whose sidewallis thinned to reduce scattering of charged particles thereon. To thinthe sidewall, the openings can have an inverted funnel or counterboreshape as shown in FIG. 3I.

The materials suitable for the first electrically conductive layer 720,the third electrically conductive layer 730 and the second electricallyconductive layer 740 may include semiconductors (e.g., silicon), andmetals (e.g., gold). The first electrically conductive layer 720, thethird electrically conductive layer 730 and the second electricallyconductive layer 740 do not necessarily have the same materials. Thefirst electrically conductive layer 720, the second electricallyconductive layer 740, the third electrically conductive layer 730 canrespectively be made from a semiconductor wafer, a semiconductor waferwith metal (e.g., gold) coating, or a dielectric plate with metal (e.g.,gold) coating. The optics elements 710 can be made from a semiconductorwafer. The optics elements 710 and the third electrically conductivelayer 730 can be made from a same semiconductor wafer, a samesemiconductor wafer with metal (e.g., gold) coating, or a samedielectric plate with metal (e.g., gold) coating. The source-conversionunit shown in FIG. 3A-FIG. 3I can help reduce or eliminate crosstalk andfield distribution deformation of the optics elements 710.

A source-conversion unit may have portions 700 in FIG. 3A-FIG. 3Istacked on one another. For example, FIG. 4A schematically shows asource-conversion unit including two of the portions 810 and 820 of FIG.3C stacked on each other. The second electrically conductive layer 740of the portion 810 upstream in the stack and the first electricallyconductive layer 720 of the portion 820 downstream in the stack can bemerged as a single layer. The optics elements 710 in the portion 810 maybe micro-deflectors; the optics elements 710 in the portion 820 may bemicro-compensators, which may comprise micro-lenses andmicro-stigmators. In alternative, the optics elements 710 along the samepath may collectively serve as a micro-compensator. The openings in thesecond electrically conductive layer 740 of the portion 820 or theopenings in the first electrically conductive layer 720 of the portion810 may serve as the openings in the electrically conductive layer 412in FIG. 1A, FIG. 1B or FIG. 1C. The sidewall of the openings may bethinned to reduce scattering of charged particles thereon. To thin thesidewall, the openings can have an inverted funnel or counterbore shapeas shown in FIG. 4A.

FIG. 4B shows another example of the source-conversion unit, which issimilar to the source-conversion unit in FIG. 4A except that the portion810 is the portion in FIG. 3I1.

FIG. 5A schematically shows a source-conversion unit including three ofthe portions 910, 920 and 930 of FIG. 3C stacked on one another. Thesecond electrically conductive layer 740 of the portion 910 upstream inthe stack and the first electrically conductive layer 720 of the portion920 in the middle of the stack can be merged as a single layer; thesecond electrically conductive layer 740 of the portion 920 in themiddle of the stack and the first electrically conductive layer 720 ofthe portion 930 downstream in the stack can be merged as a single layer.The optics elements 710 in the portions 910 and 920 may bemicro-compensators, micro-lenses and micro-stigmators; the opticselements 710 in the portion 930 can be micro-deflectors. The openings inthe first electrically conductive layer 720 of the portion 910 may serveas the openings in the electrically conductive layer 412 in FIG. 11 orFIG. 1C. The sidewall of the openings may be thinned to reducescattering of charged particles thereon. To thin the sidewall, theopenings can have an inverted funnel or counterbore shape as shown inFIG. 5A.

FIG. 5B shows another example of the source-conversion unit, which issimilar to the source-conversion unit in FIG. 5A except that the portion910 is the portion in FIG. 3H.

FIG. 6A schematically shows a source-conversion unit including three ofthe portions 910, 920 and 930 of FIG. 3D stacked on one another. Thesecond electrically conductive layer 740 of the portion 910 upstream inthe stack and the first electrically conductive layer 720 of the portion920 in the middle of the stack can be merged as a single layer; thesecond electrically conductive layer 740 of the portion 920 in themiddle of the stack and the first electrically conductive layer 720 ofthe portion 930 downstream in the stack can be merged as a single layer.The optics elements 710 in the portions 910 and 920 may bemicro-compensators, microlenses and micro-stigmators; the opticselements 710 in the portion 930 can be micro-deflectors. The openings inthe first electrically conductive layer 720 of the portion 910 may serveas the openings in the electrically conductive layer 412 in FIG. 1B orFIG. 1C. The sidewall of the openings may be thinned to reducescattering of charged particles thereon. To thin the sidewall, theopenings can have an inverted funnel or counterbore shape as shown inFIG. 6A.

FIG. 6B shows another example of the source-conversion unit, which issimilar to the source-conversion unit in FIG. 6A except that the portion930 is the portion in FIG. 3I.

FIG. 7A schematically shows a source-conversion unit including three ofthe portions 910, 920 and 930 of FIG. 3C stacked on one another (i.e.,the structure of FIG. 5A), and a portion 940 of FIG. 3D upstream to thestack of the portions 910, 920 and 930. The optics elements 710 in theportions 910 and 920 may be micro-compensators, micro-lenses andmicro-stigmators; the optics elements 710 in the portion 930 can bemicro-deflectors. The openings in the first electrically conductivelayer 720 of the portion 910 may serve as the openings in theelectrically conductive layer 412 in FIG. 1C. The sidewall of theopenings may be thinned to reduce scattering of charged particlesthereon. To thin the sidewall, the openings can have an inverted funnelshape as shown in FIG. 6A. The optics elements 710 in the portion 940may be pre-bending micro-deflectors. The sidewall of the openings in thefirst electrically conductive layer 720 of the portion 940 may bethinned to reduce scattering of charged particles thereon. To thin thesidewall, the openings can have an inverted funnel or counterbore shape.

FIG. 7B shows another example of the source-conversion unit, which issimilar to the source-conversion unit in FIG. 7A except that the portion910 is the portion in FIG. 3H.

Although the disclosure above is made with respect to multi-beamapparatuses (i.e., apparatuses that can carry out charged particle beaminspection using multiple beams of charge particles, where the chargedparticles in the multiple beams are from a single source), theembodiments may be applicable in multi-column apparatuses (i.e.,apparatuses that can carry out charged particle beam inspection usingmultiple beams of charge particles, where the multiple beams of chargeparticles are produced from multiple sources). Additional descriptionsof multi-column apparatuses may be found in U.S. Pat. No. 8,294,095, thedisclosure of which is hereby incorporated by reference in its entirety.

The embodiments may further be described using the following clauses:

1. An apparatus comprising:

a first electrically conductive layer;

a second electrically conductive layer;

a plurality of optics elements between the first electrically conductivelayer and the second electrically conductive layer, wherein theplurality of optics elements are configured to influence a plurality ofbeams of charged particles;

a third electrically conductive layer between the first electricallyconductive layer and the second electrically conductive layer; and

an electrically insulating layer physically connected to the opticselements, wherein the electrically insulating layer is configured toelectrically insulate the optics elements from the first electricallyconductive layer, and the second electrically conductive layer.

2. The apparatus of clause 1, wherein the third electrically conductivelayer comprises a plurality of holes, wherein the holes house the opticselements.3. The apparatus of any one of clauses 1-2, wherein the optics elementsare electrically insulated from the third electrically conductive layer.4. The apparatus of any one of clauses 1-3, wherein the thirdelectrically conductive layer is electrically connected to the firstelectrically conductive layer, the second electrically conductive layer,or both.5. The apparatus of any one of clauses 1-4, wherein the firstelectrically conductive layer and the second electrically conductivelayer comprise openings, wherein the openings and the optics elementscollectively form paths of the plurality of beams of charged particles.6. The apparatus of clause 5, wherein the openings have an invertedfunnel or counterbore shape.7. The apparatus of any one of clauses 1-6, wherein the thirdelectrically conductive layer is positioned between at least two of theoptics elements.8. The apparatus of any one of clauses 1-7, wherein the firstelectrically conductive layer, the second electrically conductive layer,and the third electrically conductive layer collectively form cavitiesthat accommodate the optics elements, wherein the cavities areconfigured to electrically shield the optics elements from one another.9. The apparatus of any one of clauses 1-8, wherein the electricallyinsulating layer comprises discrete portions, each of which isphysically connected to one of the optics elements.10. The apparatus of any one of clauses 1-9, wherein the electricallyinsulating layer is physically connected to the first electricallyconductive layer, the second electrically conductive layer, or the thirdelectrically conductive layer.11. The apparatus of any one of clauses 1-10, wherein the electricallyinsulating layer is configured to provide mechanical support to theoptics elements.12. The apparatus of any one of clauses 1-11, wherein the electricallyinsulating layer is positioned upstream with respect to the opticselements.13. The apparatus of any one of clauses 1-12, wherein the electricallyinsulating layer is positioned downstream with respect to the opticselements.14. The apparatus of any one of clauses 1-13, wherein the electricallyinsulating layer extends between the third electrically conductive layerand the first electrically conductive layer.15. The apparatus of clause 14, wherein the electrically insulatinglayer insulates the first electrically conductive layer from the thirdelectrically conductive layer, the second electrically conductive layer,and the optics elements.16. The apparatus of clause 14, wherein the electrically insulatinglayer comprises an electrically conductive via through the electricallyinsulating layer, wherein the electrically conductive via electricallyconnects the first electrically conductive layer to the thirdelectrically conductive layer.17. The apparatus of clause 16, wherein the electrically conductive viaencircles a cavity formed by the first electrically conductive layer,the second electrically conductive layer, and the third electricallyconductive layer and housing one of the optics elements.18. The apparatus of any one of clauses 1-13, wherein the electricallyinsulating layer extends between the third electrically conductive layerand the second electrically conductive layer.19. The apparatus of clause 18, wherein the electrically insulatinglayer insulates the second electrically conductive layer from the thirdelectrically conductive layer, the first electrically conductive layer,and the optics elements.20. The apparatus of clause 18, wherein the electrically insulatinglayer comprises an electrically conductive via through the electricallyinsulating layer, wherein the electrically conductive via electricallyconnects the second electrically conductive layer to the thirdelectrically conductive layer.21. The apparatus of clause 20, wherein the electrically conductive viaencircles a cavity formed by the first electrically conductive layer,the second electrically conductive layer, and the third electricallyconductive layer and housing one of the optics elements.22. The apparatus of any one of clauses 1-21, wherein the firstelectrically conductive layer, the second electrically conductive layerand the third electrically conductive layer comprise a semiconductor ora metal.23. The apparatus of any one of clauses 1-22, wherein the opticselements are selected from a group consisting of a lens, a stigmator, adeflector, and a combination thereof.24. The apparatus of any one of clauses 1-23, wherein the opticselements are configured to generate an electric field selected from agroup consisting of a round-lens electrostatic field, an electrostaticdipole field and an electrostatic quadrupole field.25. The apparatus of any one of clauses 1-24, wherein at least one ofthe optics elements comprises multiple poles.26. The apparatus of any one of clauses 1-25, wherein the firstelectrically conductive layer, the second electrically conductive layerand the third electrically conductive layer are configured to reducecrosstalk or field distribution deformation of the optics elements.27. The apparatus of any one of clauses 1-26, further comprising adetector configured to capture a signal produced from an interaction ofthe beams and a sample.28. The apparatus of clause 27, wherein the signal comprises secondaryelectrons or backscattered electrons, Auger electrons, X-ray, orcathodoluminescence.29. The apparatus of any one of clauses 1-28, wherein the chargedparticles comprise electrons.30. An apparatus comprising:

a first electrically conductive layer;

a second electrically conductive layer;

a plurality of optics elements between the first electrically conductivelayer and the second electrically conductive layer, wherein theplurality of optics elements are configured to influence a plurality ofbeams of charged particles;

a third electrically conductive layer between the first electricallyconductive layer and the second electrically conductive layer; and

an electrically insulating layer physically connected to the opticselements, wherein the electrically insulating layer is configured toelectrically insulate the optics elements from the first electricallyconductive layer, and the second electrically conductive layer;

wherein the electrically insulating layer extends between the thirdelectrically conductive layer and the first electrically conductivelayer, or between the third electrically conductive layer and the secondelectrically conductive layer.

31. An apparatus comprising:

a first electrically conductive layer;

a second electrically conductive layer;

a plurality of optics elements between the first electrically conductivelayer and the second electrically conductive layer, wherein theplurality of optics elements are configured to influence a plurality ofbeams of charged particles;

a third electrically conductive layer between the first electricallyconductive layer and the second electrically conductive layer;

an electrically insulating layer physically connected to the opticselements, wherein the electrically insulating layer is configured toelectrically insulate the optics elements from the first electricallyconductive layer, and the second electrically conductive layer; and

a fourth electrically conductive layer in contact with and upstream tothe first electrically conductive layer.

32. An apparatus comprising:

a first electrically conductive layer;

a second electrically conductive layer;

a plurality of optics elements between the first electrically conductivelayer and the second electrically conductive layer, wherein theplurality of optics elements are configured to influence a plurality ofbeams of charged particles:

a third electrically conductive layer between the first electricallyconductive layer and the second electrically conductive layer;

an electrically insulating layer physically connected to the opticselements, wherein the electrically insulating layer is configured toelectrically insulate the optics elements from the first electricallyconductive layer, and the second electrically conductive layer; and

a fifth electrically conductive layer in contact with and downstream tothe second electrically conductive layer.

33. A system comprising:

a source configured to produce charged particles;

an optics system configured to generate with the charged particlesmultiple probe spots on a surface of a sample and to scan the probespots on the surface, the optics system comprising the apparatus of anyone of clauses 1-32.

34. The system of clause 33, wherein the source is an electron gun.

While the concepts disclosed herein may be used for inspection on asample such as a silicon wafer or a patterning device such as chrome onglass, it shall be understood that the disclosed concepts may be usedwith any type of samples, e.g., inspection of substrates other thansilicon wafers.

The descriptions above are intended to be illustrative, not limiting.Thus, it will be apparent to one skilled in the art that modificationsmay be made as described without departing from the scope of the claimsset out below.

1-15. (canceled)
 16. An apparatus comprising: a first electricallyconductive layer; a second electrically conductive layer; a plurality ofoptics elements between the first electrically conductive layer and thesecond electrically conductive layer, wherein the plurality of opticselements are configured to influence a plurality of beams of chargedparticles; a third electrically conductive layer between the firstelectrically conductive layer and the second electrically conductivelayer; and an electrically insulating layer physically connected to theoptics elements, wherein the electrically insulating layer is configuredto electrically insulate the optics elements from the first electricallyconductive layer, and the second electrically conductive layer; whereinthe electrically insulating layer extends between the third electricallyconductive layer and the first electrically conductive layer, or betweenthe third electrically conductive layer and the second electricallyconductive layer.
 17. The apparatus of claim 16, wherein the thirdelectrically conductive layer comprises a plurality of holes, whereinthe holes house the optics elements.
 18. The apparatus of claim 16,wherein the optics elements are electrically insulated from the thirdelectrically conductive layer.
 19. The apparatus of claim 16, whereinthe third electrically conductive layer is electrically connected to thefirst electrically conductive layer, the second electrically conductivelayer, or both.
 20. The apparatus of claim 16, wherein the firstelectrically conductive layer and the second electrically conductivelayer comprise openings, wherein the openings and the optics elementscollectively form paths of the plurality of beams of charged particles.21. The apparatus of claim 20, wherein the openings have an invertedfunnel or counterbore shape.
 22. The apparatus of claim 16, wherein thethird electrically conductive layer is positioned between at least twoof the optics elements.
 23. The apparatus of claim 16, wherein the firstelectrically conductive layer, the second electrically conductive layer,and the third electrically conductive layer collectively form cavitiesthat accommodate the optics elements, wherein the cavities areconfigured to electrically shield the optics elements from one another.24. The apparatus of claim 16, wherein the electrically insulating layeris physically connected to the first electrically conductive layer, thesecond electrically conductive layer, or the third electricallyconductive layer.
 25. The apparatus of claim 16, wherein theelectrically insulating layer is configured to provide mechanicalsupport to the optics elements.
 26. The apparatus of claim 16, whereinthe electrically insulating layer extends between the third electricallyconductive layer and the first electrically conductive layer.
 27. Theapparatus of claim 26, wherein the electrically insulating layerinsulates the first electrically conductive layer from the thirdelectrically conductive layer, the second electrically conductive layer,and the optics elements.
 28. The apparatus of claim 26, wherein theelectrically insulating layer comprises an electrically conductive viathrough the electrically insulating layer, wherein the electricallyconductive via electrically connects the first electrically conductivelayer to the third electrically conductive layer.
 29. The apparatus ofclaim 28, wherein the electrically conductive via encircles a cavityformed by the first electrically conductive layer, the secondelectrically conductive layer, and the third electrically conductivelayer and housing one of the optics elements.
 30. The apparatus of claim16, wherein the electrically insulating layer extends between the thirdelectrically conductive layer and the second electrically conductivelayer.
 31. The apparatus of claim 30, wherein the electricallyinsulating layer insulates the second electrically conductive layer fromthe third electrically conductive layer, the first electricallyconductive layer, and the optics elements.
 32. The apparatus of claim30, wherein the electrically insulating layer comprises an electricallyconductive via through the electrically insulating layer, wherein theelectrically conductive via electrically connects the secondelectrically conductive layer to the third electrically conductivelayer.
 33. The apparatus of claim 32, wherein the electricallyconductive via encircles a cavity formed by the first electricallyconductive layer, the second electrically conductive layer, and thethird electrically conductive layer and housing one of the opticselements.
 34. The apparatus of claim 16, further comprising a detectorconfigured to capture a signal produced from an interaction of the beamsand a sample.
 35. The apparatus of claim 34, wherein the signalcomprises secondary electrons or backscattered electrons, Augerelectrons, X-ray, or cathodoluminescence.